engleski

Correlation Between Distance of the Perturbing Groups and Enantioselectivity of the Lipase Catalyzed Acylation of Acyclic sec Alcohols

Study of kinetic resolutions of racemic sec alcohols 1-4, by acetylation to 5-8 with a series of microbial lipases in n-hexane, revealed the broadest selectivity of Geotrichum candidum (GCL) and Candida cylindracea (CCL(S), from Sigma) lipase in accepting these conformationaly flexible substrates. Surprisingly, for both lipases non-monotonous correlation between E-value and the distance (n) of perturbing groups in 1-4 is observed. GCL preferred small and large substrates, whereas CCL preferred medium-size substrates. For GCL lipase a remarkable turnover of enantioselectivity was observed on going from 1-3 to 4, revealing that relative steric requirements of the larger phenoxy group vs. smaller methyl group does not control the enantioselective bias in the latter. For Candida cylindracea (CCL(A), from Amano) lipase the conversion and E vary in a monotonous fashion from smaller to larger substrates. (C) 1997, Elsevier Science Ltd.

Organic-solvents. Candida-rugosa. Rule

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